Work will be continued on the purification of the primary intracellular serine protease of Bacillus subtilis. Attempts will be made to stabilize this rather labile activity by reacting it with C14- phenyl methyl sulfonyl fluoride; reactivation will be tried by using formyl hydroxymate. Additionally affinity chromatography on casein- acrylamide beads and selective precipitation with antibodies against Bacillopeptidase F will be tested. Two thiolester substrates have been made one of which, N-benzoyl- L-tryosine thiobenzyl ester, seems to be a good substrate for the intracellular protease. Work is proceeding on the synthesis of some additional thiolesters in order to find ones with greater solubility and improved stability in aqueous solution.